Managing urban nutrient biogeochemistry for sustainable urbanization

• Characteristics of nutrient cycling within urban and natural ecosystem are compared.
• We examine how urbanization effects food sourced Nitrogen and Phosphorus metabolism.
• Nutrient footprint and calculation method is introduced from lifecycle perspective.
• Three system approaches to mend the broken biogeochemical cycling are proposed.
• Coupling nutrient consumption with production can balance nutrient cycling.

Urban ecosystems are unique in the sense that human activities are the major drivers of biogeochemical processes. Along with the demographic movement into cities, nutrients flow towards the urban zone (nutrient urbanization), causing the degradation of environmental quality and ecosystem health. In this paper, we summarize the characteristics of nutrient cycling within the urban ecosystem compared to natural ecosystems. The dynamic process of nutrient urbanization is then explored taking Xiamen city, China, as an example to examine the influence of rapid urbanization on food sourced nitrogen and phosphorus metabolism. Subsequently, the concept of a nutrient footprint and calculation method is introduced from a lifecycle perspective. Finally, we propose three system approaches to mend the broken biogeochemical cycling. Our study will contribute to a holistic solution which achieves synergies between environmental quality and food security, by integrating technologies for nutrient recovery and waste reduction.